The present invention relates to a silver halide photothermographic light-sensitive material and in particular to a silver halide photothermographic light-sensitive material (hereinafter, also referred to as a silver halide photothermographic material or simply as photothermographic material) having minimal flaws and coating defects in its undercoating layer.
Recently, the wet development process of photographic material, which has been widely used so far, is overcoming problems such as to reducing photographic processing effluents, with respect to a social trend of strong requirement for environmental care. Attempts to minimize the amount of processing effluents have been made, for example, by reducing replenishing rates, solidifying processing chemicals or recycling processing solutions. Silver halide photothermographic materials, which can adapt to dry processing rather than wet processing, have been developed under the foregoing circumstance. A silver halide photothermographic material called xe2x80x9cDry Silverxe2x80x9d including a silver halide, reducing agent and silver salt of a fatty acid is coming to be used in some areas of photographic materials, because of using no liquid and producing no waste.
The foregoing silver halide photothermographic material can be developed by heating at 80 to 140xc2x0 C. after exposure without being further subjected to any other post-processing and which is an environmentally friendly photographic material.
Silver halide photothermographic materials are expected to undergo further development due to its ease of handling, however it has been necessary to solve the problem of some defects which were not a problem in wet processing silver halide light-sensitive photographic materials. Specifically, in the case of medical X-ray silver halide light-sensitive materials, a silver halide photothermographic material free of abrasion mark, adhesion matters or the like, which may lead to misdiagnosis of an area of focus in radiography of a living organism has been required.
Extensive study by the inventors to solve the foregoing problems has revealed that some of the aforementioned shortcomings are due to characteristics of an undercoating layer. Further, it was proved that problems during the drying of the undercoating layer are related to white spot defects (whitish spots caused in a light-sensitive layer) of silver halide photothermographic materials which appear after heat development. The inventors have proved that some flaws or cut-off in the undercoating layer are produced while transporting the web after coating of the undercoating layer and the white spot defects are assumed to be produced from the results thereof: unevenness of the undercoating layer; minute protrusions of the support produced before the coating of the silver halide photothermographic light-sensitive layer due to the winding pressure after the under-coated support has been wound up; transfer of matter dropped off from the undercoating layer and the like; or uneven surface of the photographic material produced after coating of the silver halide photothermographic light-sensitive layer. Factors causing no problem in wet processable conventional silver halide photographic light-sensitive materials may cause aforementioned troubles in case of silver halide photothermographic materials. There has been strongly desired development of a technique for improving such defects in silver halide photothermographic materials.
Accordingly, it is an object of the invention to provide a silver halide photothermographic material, in which the undercoating layer is resistant to abrasion and produces no dropped-off matter, nor causing staining in the coating process, thereby minimizing white spotting defects. The white spots referred in the invention are portions where the silver halide light-sensitive layer becomes thinner, producing a fine portion giving a lower image density relative to the surrounding normal portion.
The inventors have found that fine particles such as a matting agent used in an undercoating layer may collapse or drop off when the support web is coated with an undercoating layer and then transported by the rolls, which produces a dug hole, sticks to the undercoating layer or scratches the undercoating layer again, and these kinds of defects result in white spotting defects or abrasion marks. Therefore the inventors have found fine particles to be more suitable for photothermographic materials, and have succeeded in developing a photothermographic material including the undercoating layer using these fine particles.
The invention comprises the following structures.
Structure 1:
A silver halide photothermographic light sensitive material comprising a support having thereon an undercoating layer and a light-sensitive layer containing a light-sensitive silver halide, an organic silver salt, a reducing agent and a binder, wherein the undercoating layer contains fine particles having a mean primary particle size of 0.01 to 1.6 xcexcm and satisfying the following equation:
1xe2x89xa6(r2/r1)xe2x89xa61.4
wherein r1 and r2 are respectively an inscribed circle radius and a circumscribed circle radius of each of projected images of the fine particles obtained by a microscope, and (r2/r1) is an average value of r2/r1 of 500 projected image of the fine particles randomly selected from the whole fine particles.
Structure 2:
The silver halide photothermographic light-sensitive material of Structure 1, wherein the undercoating layer contains the fine particles of 10 to 100 in an area of 100 xcexcm square and has a center-line mean roughness (Ra) of not more than 0.015 nm.
Structure 3:
The silver halide photothermographic light-sensitive material of Structure 1, wherein the fine particles have a variation coefficient of primary particle size of not more than 0.25.
Structure 4:
The silver halide photothermographic light-sensitive material of Structure 1, wherein the fine particles are inorganic fine particles having a surface modified with an alkoxide.
Structure 5:
The silver halide photothermographic light-sensitive material of Structure 1, wherein the fine particles are nonporous.
Structure 6:
The silver halide photothermographic material of Structure 1, wherein the undercoating layer contains a hydrophilic polyester resin.